1. Field of the Invention
The present invention relates generally to a sensor network including reference nodes and sensor nodes. More particularly, the present invention relates to a sensor node locating method and system that enable a sensor node to receive location information signals with successively varying signal strength from plural reference nodes and to compute the coordinates of the location of the sensor node and an associated error.
2. Description of the Related Art
It is expected that various new services will be created in the near future through ubiquitous computing or ubiquitous networks. In particular, location-based services, based on identification of locations of objects, such as persons and things anytime anywhere, are on the rise as important services. Location-based services using location and geographical information have demonstrated their usefulness in various fields, and are advancing beyond a particular business area to technologies heightening the value of an entire country. Most location-based services have been developed using the Global Positioning System (GPS), and ignored shadow areas. Currently, research is underway to provide location-based services in shadow areas, with the help of existing massive network infrastructure and digital equipment. In particular, active research is in progress by many in the field, particularly with regard to position locating techniques based on sensor networks because of their wide application areas.
Sensor network-based locating techniques are used in diverse application areas including logistics, security, home automation, factory automation, and building automation, and are particularly effective for services utilizing locations of individual persons and things such as protection of elderly and disabled persons or children, identification of positions of soldiers in battle, rescue of firefighters isolated or lost in the scene of a fire, and medical treatment. The content of information to be collected from sensor networks tends to be growing, and, in particular, identification of the location of a person wearing a sensor or a thing with an attached sensor has become important.
Infrared rays, ultrasonic waves and radio frequency (RF) waves are used for locating positions of objects such as persons. RF-based position location may result in a large error in the determined position and the actual position, because RF signals are very sensitive to external environmental conditions. RF-based locating services require accuracy in obtained location data. Hence, there is a need to provide a technique that increases accuracy in position locating so that an RF-based locating system can extend the service area to cover shadow areas.